Flush Syringe Having Anti-Reflux Features

ABSTRACT

An I.V. flush syringe assembly includes a barrel having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end with a passageway therethrough in fluid communication with the chamber. An elongate plunger having a proximal end, a distal end and a flexible stopper is slidably positioned in fluid-tight engagement with the inside surface of the barrel for drawing fluid into and out of the chamber by movement of the stopper relative to the barrel. The barrel includes anti-reflux structure for holding said stopper in a partially deflected position after fluid has been delivered from the chamber and the stopper is being force against the distal end of the chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

Noon This is a continuation of pending U.S. application Ser. No.14/722,488, filed May 27, 2015, which is a divisional of pending U.S.application Ser. No. 10/530,817, filed Apr. 8, 2005, and issued on Jul.7, 2015, as U.S. Pat. No. 9,072,844, which is the National Phase entryof International Application No. PCT/US03/29918, filed Sep. 23, 2003,which claims priority from U.S. Provisional Application No. 60/418,053,filed Oct. 11, 2002.

BACKGROUND OF THE INVENTION

The present invention relates to syringe assemblies and particularly tosyringe assemblies for use in I.V. flush procedures.

An I.V. catheter is a commonly used therapeutic device. Many patients,in accordance with their therapy, have an I.V. catheter connected to avein ready for use in various procedures or in fluid communication withan I.V. system for infusing liquids and medication. Many I.V. sets haveI.V. ports which are in fluid communication with a catheter and allowaccess for the purpose of injecting medication into the patient, and foruse in flushing techniques to maintain catheter integrity. Healthcarefacilities have flushing protocols which depend on the amount of timethe catheter will remain in the patient and the type of catheter beingused. For example, a peripherally inserted central catheter (PICC) is along flexible catheter, which is typically inserted into the centralvenous system (optimally with the tip terminating in the superior venacava) via the superficial veins of the antecubital fossa. PICC lines aredesigned for use when intermediate or long-term therapy is prescribed.

These catheter lines must be periodically flushed with saline flushsolution and/or heparin lock flush solution depending on the protocol.Among other things, flushing saline solution removes blood from thecatheter and heparin helps prevent the formation of future blood clots.The most common I.V. ports are covered by pierceable septums or pre-slitseptums and are known in the art and sometimes referred to as “PRN” fromthe Latin pro re rata meaning “as the need arises”. The septum ispreferably made of rubber or another elastomeric material which permitsinsertion of a sharp needle cannula in order to infuse fluids into or towithdraw fluids from the catheter. Upon withdrawal of the needle cannulathe septum seals itself. Ports having pre-slit septums are used withblunt cannula. Typically, the blunt cannula is attached to a syringe andthe syringe is moved to place a gentle pressure on the pre-slit septumwhich is forced open by the blunt cannula to establish fluidcommunication. Also, some I.V. sets have access valves which areresponsive to the frusto-conically shaped tip of a syringe barrel forallowing fluid communication between the interior of the syringe and thecatheter.

Catheters are flushed using syringe assemblies filled with variousfluids. In some cases, different fluids are injected sequentially inaccordance with the protocol. For example, a saline solution followed byan anticoagulant such as heparin. The size of the syringe used to flushI.V. lines varies by various factors including the size and length ofthe catheter. Typically syringes of 1 ml, 3 ml, 5 ml and 10 ml volumeare used.

It is important in the flush procedure not to draw blood back into thecatheter where it can clot and seal the catheter, commonly referred toas “reflux”. In order to prevent blood reflux into the catheter the useris encouraged to maintain a positive pressure in the line during theflush procedure. This may involve slowly withdrawing the syringe andcannula from the I.V. port while still applying pressure to the syringeplunger rod during the flush procedure. When using a syringe with anelastomeric stopper, the stopper is often compressed when it contactsthe distal end of the syringe barrel at the completion of the flushprocedure. When a user relieves the pressure to the plunger after theflush procedure is completed, the stopper will expand back to its normalsize drawing liquid from the catheter into the syringe barrel. This isundesirable, since it can cause blood to enter the catheter at thecatheter distal end (reflux).

Therefore there is a need for simple, straight forwardeasy-to-manufacture syringe assemblies which reduce or eliminate refluxof blood into the catheter during and after the flushing procedure hasoccurred without changing flush protocols and procedures.

SUMMARY OF THE INVENTION

The present invention is directed to a syringe having a compressiblestopper. The stopper is held in position at the distal end of the barrelat the completion of the flush procedure. The stopper is held in acompressed form, by structure resisting its expansion. Since expansionof the stopper is substantially prevented at the completion of the flushprocedure, reflux of blood into the catheter is minimized and/oreliminated.

An I.V. flush syringe assembly includes a barrel having an insidesurface defining a chamber for retaining fluid, an open proximal end anda distal end including a distal wall with an elongate tip extendingdistally therefrom having a passageway therethrough in fluidcommunication with the chamber. A plunger including an elongate bodyportion having a proximal end, a distal end with a flexible stopperslidably positioned in fluid-tight engagement with the inside surface ofthe barrel for drawing fluid into and driving fluid out of the chamberby movement of the stopper relative to the barrel. The elongate bodyportion of the plunger extends outwardly from the open proximal end ofthe barrel. The I.V. flush syringe includes anti-reflux means forholding the stopper in a partially deflected position when fluid hasbeen delivered from the chamber and the stopper is in contact with thedistal wall of the barrel. Such anti-reflux means provide structure onthe stopper and/or barrel to hold the stopper in a partially deflectedposition to minimize or eliminate reflux by preventing the stopper frommoving proximally and drawing blood into the catheter.

The anti-reflux structure can include the stopper having an outwardlyprojecting rib and the inside surface of the barrel having a recess forreceiving the rib when the stopper is in contact with and partiallycompressed against the distal wall of the barrel. The projection on thestopper may include one or more annular ribs and the recess in thebarrel may include one or more annular grooves for accepting the ribs.

The anti-reflux structure may also include a contact area on the insidesurface of the barrel at the distal end of the barrel. The contact areahas a higher coefficient of friction than the inside surface of thebarrel which is outside of the contact area. The contact area is forengaging the stopper when the stopper is in contact and compressedagainst the distal wall of the barrel. The contact area may include aplurality of annular deformations. These deformations may be projectionson the inside surface of the barrel.

A method of flushing a catheter of the present invention comprises thesteps of providing a syringe assembly including a barrel having aninside surface defining a chamber for retaining fluid, an open proximalend and a distal end including a distal wall with an elongate tipextending distally therefrom having a passageway therethrough in fluidcommunication with the chamber, a plunger including an elongate bodyportion having a proximal end, a distal end and a flexible stopperslidably positioned in fluid-tight engagement with the inside surface ofthe barrel for drawing fluid into and driving fluid out of the chamberby movement of the stopper relative to the barrel, the elongate bodyportion of the plunger extending outwardly from the open proximal end ofthe barrel, a quantity of flush solution in the chamber, and anti-refluxmeans for holding the stopper in a partially deflected position when theflush solution has been delivered from said chamber and the stopper isin contact with the distal wall. The method further includes providing acatheter having a proximal end, a distal end and a passagewaytherethrough and a housing having a hollow interior connected to thecatheter and in fluid communication with the passageway, the housinghaving an access valve for allowing fluid communication with the hollowinterior. The method further includes the additional steps of: placingthe distal end of the catheter in a blood vessel; engaging the elongatetip of the barrel with the access valve so that the passageway of thesyringe barrel is in fluid communication with the hollow interior of thehousing; applying force to the plunger to move the stopper in a distaldirection with respect to the barrel so that the flush solution in thechamber flows through the passageway into the hollow chamber of thehousing and through the passageway of the catheter; and continueapplying force to the plunger until the stopper contacts and pressesagainst the distal wall of the barrel and is held in a partiallydeflected position by anti-reflux means.

An alternate method includes the step of attaching a needle assembly tothe elongate tip of the barrel. The needle assembly includes a cannulahaving a proximal end, a distal end and a lumen therethrough and a hubhaving an open proximal end containing a cavity and a distal endattached to the proximal end of the cannula so that the lumen is influid communication with the cavity. The attachment of the needleassembly to the barrel is through frictional engagement between thecavity in the hub and the elongate tip. This alternative method is usedwith a catheter having a proximal end, a distal end and a passagewaytherethrough and a housing having a hollow interior connected to thecatheter and in fluid communication with the passageway of the catheter.The housing further includes a septum for allowing fluid communicationwith the hollow interior. Fluid communication is established by forcingthe distal end of the cannula through the septum so that the lumen ofthe cannula is in fluid communication with the hollow interior of thehousing. Also, the cannula may be permanently attached to the needle tipwithout the use of a hub.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a syringe assembly according to oneembodiment of the invention.

FIG. 2 is a partially cross-sectioned side-elevational view of thesyringe of FIG. 1 with a needle assembly attached.

FIG. 3 is an enlarged partial cross-sectional side elevation view of thedistal end of the syringe assembly of FIG. 2.

FIG. 4 is an enlarged partial cross-sectional side-elevational view ofthe distal end of the syringe assembly of FIG. 2 with the stopperpositioned in its distal-most position after flush solution has beendelivered.

FIG. 5 is a side-elevational view illustrating the syringe assembly inuse with a catheter injection site.

FIG. 6 is a perspective view of a syringe assembly according to anotherembodiment of the invention.

FIG. 7 is a partially cross-sectioned side-elevational view of thesyringe assembly of FIG. 6.

FIG. 8 is an enlarged cross-sectional side elevation view of the distalend of the syringe assembly of FIG. 7.

FIG. 9 is an enlarged cross-sectional side elevational view of thedistal end of the syringe assembly of FIG. 7 with the stopper positionedin its distal-most position after flush solution has been delivered.

DETAILED DESCRIPTION

FIGS. 1-4 show a syringe 20 according to the present invention generallycomprising a barrel 22, a plunger 24. Barrel 22 has a generally elongatebody including an open proximal end 28 having finger grips 29, a distalend 30 and an inside surface 32 defining a fluid chamber 34. Insidesurface 32 includes a generally annular recess 35 towards distal end 30.Distal end 30 further includes a tip 36 having a passageway 38 in fluidcommunication with the chamber 34. The distal end of barrel 22preferably, but does not necessarily include a locking luer type collar40 concentrically surrounding tip 36. The inside surface of the collarincludes at least one thread 41. A cannula 26 includes a proximal end42, a distal end 44 and a lumen 46 therethrough. The distal end mayinclude a sharp tip or a blunt tip 48 as shown. The cannula may beconnected directly to the tip of the syringe barrel to establish fluidcommunication between the lumen and the chamber. Also, the cannula maybe part of a needle assembly 27 including a hub 37 having an openproximal end 39 containing a cavity 43 and a distal end 45 attached tothe proximal end of the cannula so that the lumen of the cannula is influid communication with the cavity. The cavity of the hub can beremovably frictionally engaged to the tip of the barrel as illustratedin FIGS. 2-4.

Plunger 24 includes a proximal end 50 having a flange 51 and a distalend 52. A flexible stopper 54 is disposed on the distal end of plunger24.

Stopper 54 includes at least one annular rib and in this embodimentincludes a proximal rib 56, a middle rib 58 and a distal rib 60. Thestopper comprises any flexible resilient material suitable for providingsealing characteristics while under compression. For example, thestopper may be made of thermoplastic elastomers, natural rubber,synthetic rubber and the like.

In operation, the syringe 20 is connected to a hypodermic needleassembly and filled with flush solution using known methods. The flushsolution may be any solution intended for flushing. It is preferred thatthe flush solution be selected from the group consisting of saline flushsolution and heparin lock flush solution. These solutions are known inthe art and readily available. An example of a saline flush solution is0.9% Sodium Chloride USP. An example of a heparin lock flush solution is0.9% sodium Chloride with 100 USP units of Heparin

Sodium per ml or 10 USP units of Heparin Sodium per ml. The syringe withneedle assembly attached is used to pierce the pierceable septum or ablunt cannula may be inserted into a pre-split septum of a vialcontaining flush solution and the flush solution is drawn into thesyringe barrel by pulling plunger rod flange 51 in the proximaldirection while holding barrel 22, to draw fluid through the needlecannula into the fluid chamber 34.

Alternatively, the syringe may be filled with flush solution during themanufacturing of the syringe via a sterile filling method. Suchprefilled syringes may be supplied with a tip cap, such as tip cap 23releasably connected to tip 36 sealing passageway 38. It is preferredthat the tip cap is formed of material selected from the group ofthermoplastic materials and elastomeric materials such as natural andsynthetic rubber and thermoplastic elastomers.

The syringe is now ready for use in flushing a catheter of an I.V. set.I.V. sets can be very complicated and may include multiple injectionports, a valve and/or other components. For the purpose of illustratingthe present invention a simplified I.V. set 64 is illustrated in FIG. 5.I.V. set 64 comprises an I.V. site 65 which includes a housing 67 havinga hollow interior 68 and a septum 69 at its proximal end. A catheter 70having a conduit therethrough extends from the distal end of thehousing. For this I.V. set, septum 69 is pre-slit for use with bluntcannula. The I.V. site may have a pierceable septum or a valve havingstructure for accepting the syringe barrel tip and being activated bythe insertion of the tip to establish fluid communication with thecatheter, such as the valve taught in U.S. Pat. No. 6,171,287.

Blunt tip 48 of cannula 26 may be inserted through pre-split septum 69of I.V. set 64. Alternatively, a sharp tip of a needle cannula may beused to pierce a septum that it not pre-split, or the tip of the barrelmay be engaged with a valve in the IV site. This establishes fluidcommunication between the interior 68 of the I.V. set and the chamber ofthe syringe barrel. The syringe barrel 22 is preferably held via fingergrips 29. Pressure is then applied to flange 51 of the plunger, forexample by a thumb, in the distal direction. This moves the plunger 24having the stopper 54 on its distal end, forcing the liquid such asflush solution 35 in the chamber 34 out of the chamber, through cannula26 and into interior 68 of the I.V. set and then through catheter 70.

Referring to FIG. 4, the position of the plunger and stopper at thecompletion of the flush procedure is shown. As shown, the flange 51 doesnot contact the proximal end of the barrel at the completion of theflush procedure. Stopper 54 is now compressed. Distal rib 60 of thestopper is received within recess 35 of the barrel. Distal rib 60 fitswithin the recess 35 preferably via a friction fit or an interferencefit. Thus, the stopper 54 is held in position at the distal end of thebarrel 22. This, in turn, holds the plunger 24 within the barrel.Therefore, reflux of liquid, including blood, into the catheter isprevented or minimized since the stopper is held in a compressed formand will not withdraw into the proximal direction.

It is within the purview of the present invention to include additionalrecesses at the distal end of the barrel to receive the middle rib andthe proximal rib. In such an embodiment, the recesses would be spacedapart in order to receive the ribs when the stopper is in a compressedform, typical at the end of the flush procedure.

FIGS. 6-9 shown another embodiment of the invention where like elementsare similarly numbered. In this embodiment of the invention, syringeassembly 120 includes plunger 24 and barrel 122. A needle assembly 127includes cannula 126 having a sharp distal end and hub 137 attached todistal end 130 of the barrel. Inside surface 132 of syringe barrel 122includes a contact area 162. The contact area may be, for example, oneor more discontinuities, and/or a roughened portion of the insidesurface. In operation, after the flush procedure has occurred, thestopper 54 is compressed at the distal end of the barrel within contactarea 162 of the barrel. The contact area restrains the stopper frommoving in the proximal direction. Therefore, stopper 54 is frictionallyrestrained by the contact area 162, holding stopper 54 and plunger 24within the barrel. The force required to overcome the friction betweenthe stopper 54 and contact area 162 is more than the force required toovercome the friction between the stopper and the inside surface thebarrel outside of the contact area. The force between the stopper andthe contact area is sufficient to hold the stopper in a partiallycompressed state after the stopper contacts the distal end of thechamber. Thus, the stopper 54 is restrained from expanding out of itscompressed form thereby preventing or minimizing reflux.

Although the invention herein has been described with reference toparticular embodiments it is to be understood that these embodiments aremerely illustrative of the principles and applications of the presentinvention. It is therefore to be understood that numerous modificationsmay be made to the illustrative embodiments and that other arrangementsmay be devised without departing from the spirit and scope of thepresent invention.

What is claimed is:
 1. An I.V. flush syringe assembly comprising: abarrel having an inside surface defining a chamber for retaining fluid,an open proximal end and a distal end including a distal wall with anelongate tip extending distally therefrom having a passagewaytherethrough in fluid communication with said chamber, said insidesurface having distal annular recess at the distal end; a plungerincluding an elongate body portion having a proximal end, a distal endand a flexible stopper slidably positioned in fluid-tight engagementwith said inside surface of said barrel for drawing fluid into anddriving fluid out of said chamber by movement of said stopper relativeto said barrel, said elongate body portion extending outwardly from saidopen proximal end of said barrel and said flexible stopper including adistal annular rib, a middle annular rib and a proximal annular ribwherein said distal annular rib is configured to be received within saidannular recess at said distal end of said barrel via a friction fit oran interference fit upon completion of a flush procedure, therebyholding said stopper in compressed form and preventing withdrawal ofsaid stopper in a proximal direction.
 2. The I.V. flush syringe assemblyof claim 1, wherein the inside surface of the barrel further comprises amiddle annular recess configured to receive the middle annular rib uponcompletion of the flush procedure when the stopper is held in compressedform.
 3. The I.V. flush syringe assembly of claim 2, wherein the insidesurface of the barrel further comprises a proximal annular recessconfigured to receive the proximal annular rib upon completion of theflush procedure when the stopper is held in compressed form.
 4. The I.V.flush syringe assembly of claim 1, further comprising a flush solutionin the chamber and a tip cap releasably connected to the tip to seal thepassageway.
 5. The I.V. flush syringe assembly of claim 4, wherein theflush solution is a saline flush solution or a heparin lock flushsolution.
 6. The I.V. flush syringe assembly of claim 1, wherein theflexible stopper is made of thermoplastic elastomers, natural rubber, orsynthetic rubber.
 7. A method of preventing or minimizing reflux afterflushing a catheter comprising the steps of: (a) providing an I.V. flushsyringe assembly according to claim 1 having a quantity of flushsolution in the chamber; (b) providing a catheter having a proximal end,a distal end and a passageway therethrough and a housing having a hollowinterior connected to said catheter and in fluid communication with saidpassageway of said catheter; (c) placing said distal end of saidcatheter in a blood vessel; (d) establishing fluid communication betweensaid passageway of said barrel and said hollow interior of said housing;(e) applying force to said plunger to move said stopper in a distaldirection with respect to said barrel so that said flush solution insaid chamber flows through said passageway of said barrel into saidhollow interior of said housing and through said passageway of saidcatheter; (f) continuing to apply force to the plunger until saidstopper contacts, and is compressed against, said distal wall of saidbarrel, such that the distal annular rib of the stopper is receivedwithin the distal annular recess and held in compressed form, therebypreventing withdrawal of the stopper in a proximal direction.
 8. Themethod of claim 7, wherein the inside surface of the barrel furthercomprises a middle annular recess and the middle annular rib is receivedin the middle annular recess when the stopper is held in compressedform.
 9. The method of claim 8, wherein the inside surface of the barrelfurther comprises a proximal annular recess and the proximal annular ribis received in the proximal annular recess when the stopper is held incompressed form.